People on the exmormon forum were talking about what to do when you're not comfortable praying over communal meals, but the people you have over expect you to.
This is the idea I came up with:
I would like to express my personal thanks to the migrant farm workers and nonhuman animals, who sacrificed to bring us this meal. We will now have a moment of silence, if you'd like to say a prayer for or otherwise remember them.
I try to practice a personal mindfulness ritual before every snack, drink, and meal, and I think this is the closest I've come to translating that into a "saying grace" kind of blessing.